Safety device for rolling mills

ABSTRACT

In a rolling mill, particularly a multistand rolling mill for the drawing of metal rods and the like, the improvement consisting in a safety device provided on at least the last stand and consisting of the shearable means securing the outlet guide for the rolled material to the same stand, whereby when the shearable fixing means are subjected to a thrust greater than a predetermined value, the outlet guide is separated from the rolling stand and engages switch means by which the drive to the rolling stands is disengaged.

United States Patent [191 Properzi Aug. 27, 1974 SAFETY DEVICE FOR ROLLING MILLS Ilario Properzi, Via Cosimo Del Frame, 10, Milan, Italy Filed: July 9, 1973 Appl. No.: 377,303

Inventor:

[30] Foreign Application Priority Data July 22, 1972 Italy 27322/72 US. Cl. 72/5 Int. Cl..... B2lb 39/14, B2lb 35/00, Fl6p 7/00 Field of Search 72/4, 3, 5, 227, 250

[56] References Cited UNITED STATES PATENTS 1,599,045 9/1926 Good 72/4 3,651,674 3/1972 Petit 72/5 Primary Examiner-Milton S. Mehr Attorney, Agent, or FirmDiller, Brown, Ramik & Wight 6 Claims, 5 Drawing Figures PAIENIEB Anne-1 I974 SHEET 20F w This invention relates to a safety device for rolling mills, in particular for multi-stand rolling mills in which metal rod or the like is drawn, designed to interrupt the transmission of motion from the motor to the rolling stands when jamming or abnormal overloads occur at the rolling stands.

In modern rolling mills the rolling stands are notably rotated at a predetermined rotational speed by a kinematic gear chain, each shaft of which drives a single rolling stand. The motor is connected to the drive pinion of the gear chain by means of a clutch preferably of electromagnetic type.

Up to the present time the safety measures adopted for preventing serious damage to the said kinematic chain consiste in making the coupling between each rolling stand and the relative drive shaft in the form of a safety coupling with shear pins. in this manner, if the predetermined torque limit is exceeded for any reason in any of the rolling stands, breakage occurs of the safety pin or pins of the said coupling. This latter is made in such a manner that the breakage of the safety pin gives rise to the movement of a tooth which then acts on a switch which in its turn opens'the electromagnetic coupling of the motor. When themotor is disconnected, the rolls of the rolling stands are free to stop under the braking action of the rolling forces. In this solution the motor is decoupled by means of the electromagnetic joint because, on account of the high moment of inertia of the motor rotor, the stopping time for the rolling mill is thus reduced to a minimum. As an alternative to this system the switch operated by the breakage of the safety pins of the coupling may act so as to simply interrupt the supply of current to the motor, possibly linking this to the closure of a suitable brake so as to reduce the stopping time of the rolling mill.

Although the aforementioned system givesfairly satisfactory results with regard to the prevention of damage to the kinematic chain, it however gives rise to certain disadvantages regarding the rolling stands and in particular the rolls.

As stated, the operation of the safety device occurs on the occasion of abnormal jamming or overload at the rolls. Normally, a rolling stand comprises a housing constructed in such a manner as to be able to house within it the rolls with their relative shafts, bearings and drive gears. Each housing also comprises suitable inlet and outlet guides for the material being rolled; the purpose of the former is to ensure that the material arrives in the correct position at the rolls whereas the outlet guides control the rolled material leaving the stand so that it becomes directed towards the next stand or collection device (coiler, if dealing with the last stand). When the rolling mill is well adjusted and both the operating conditions and the conditions of the material are regular, the material being rolled passes from one stand to the next, reducing its own cross-section, guided by the said guides.

When a stand goes out of adjustment or, more frequently, difficulties arise in the coiler, the rolled material (the rod) finds it difficult to proceed, i.e., if the winding pull of the coiler is not present the last stand itself has to push the material out, which can be done only within certain limits.

In fact, if the resistance to the advancement of the material increases beyond a certain limit, the rod leaving the stand becomes subjected to a combined bending and compressive stress which at a certain point causes the rod to buckle immediately after the exit from the rolls. Under these conditions the rod does not enter the outlet guide, hits against the guide and fills all the cavities between the casing, the rolls and the guide.

The material which is thus building up outside the guide (which in jargon is called flower) continues to increase, exerting an increasingly greater braking action on the rolls; this braking action isthe cause of the abnormal increase in the force required for operating that particular stand and which, having reached a certain value, causes breakage of the safety pin of the coupling between the stand and the drive transmission.

It is evident that the formation of the flower may easily damage the working surface of the rolls, due to rubbing of the roll against the material constituting the flower.

A safety device for rolling mills has now been discovered, and constitutes the object of the present invention, which, while maintaining the advantages of the systems of the previous technique, eliminates the aforementioned disadvantages, the device being characterised in that the outlet guide for the rolled material, of at least the last stand, and preferably of each stand of the rolling mill, is fixed to the housing of the respective rolling stand by fixing means arranged to allow the guide to separate from the housing when said fixing means are subjected to a thrust greater than a predetermined value.

The main advantage of the safety device according to this invention is that strong braking actions on the rolls do not need to be reached (such as those that were necessary to cause breakage of the safety pin or pins of the coupling upstream of the rolling stand in devices according to the previous technique), but the separation or expulsion of the outlet guide from the corresponding housing of the rolling stand may take place and in fact takes place as soon as the material, instead of passing regularly into the guide, begins to press against its edge.

A further advantage of the device according to the invention is that the braking action of the flower on the roll begins to reach high values when the material has filled the entire cavity between the rolls and the guide, whereas the expulsion of the guide according to the present invention may take place a considerable and predetermined time before the breakage of the safety pin or pins of the drive coupling mounted upstream of the rolling stand. A further advantageous aspect of the device according to the present invention is that the expulsion of the guide avoids large build-up of the material because the space occupied by the expelled guide becomes occupied by the material which the rolls still continue to roll before the stoppage of the entire rolling mill.

These and other aspects and advantages of the present invention will be more evident from the following description given by way of non-limiting example, with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic representation of a rolling mill to which the device according to the present invention is applied;

FIGS. 2 and 3 are two vertical sections through a conventional rolling mill, in the nonnal working condition and with the flower formation respectively;

FIG. 4 is a diagrammatic partial sectional view of a rolling stand comprising a first embodiment of the safety device according to the present invention, and

FIG. 5 is a view analogous to FIG. 4 of another embodiment of the device according to the present invention.

FIGS. 1 to 3 show a seven stand rolling mill (it being understood that the number of rolling stands does not constitute a limitation) comprising a motor which, by way of the electromagnetic clutch 11, is connected to the drive pinion 12 of a gear chain indicated overall by the reference numeral 13. Each rolling stand 14 is coupled to the relative drive shaft by means of a coupling 15, preferably a shear pin safety coupling of the type conventionally used in rolling mills.

The rolling stand shown in FIGS. 2 and 3 is of the two roll type and comprises a housing 16 constructed so as to house within it both the rolls l7, driven by the shafts l8, and the relative shafts, bearings and drive gears, together with the inlet and outlet guides, 19 and 20 respectively, for the material 21 subjected to rolling.

FIG. 3 shows the state of the stand of FIG. 2 while the said flower" of rolled material is being formed.

FIG. 4 shows part of a rolling stand 22, of the three roll type disposed at 120 about the axis of the material being rolled, comprising a housing 23, in which the rolls 24 (of which only one is shown), an inlet guide (not shown) for the material to be rolled and an outlet guide 25 are housed. The guide 25 is fixed to the housing 23 by screws 26 of predetermined fracture value, which is created by means of a suitable groove 27 made under their heads. A tooth or chamfered collar 28 is fixed to the guide 25 by screws 29, with the purpose of operating the microswitch 30 by engaging with its relative control 31 when the guide 25 and hence the collar 28 are expelled from the housing following the shearing of screws 26. From the figure it will be clear that the screws 26 are screwed into the housing 23, but pass freely through the aligned holes 32 both in the guide 25 and in the collar 38. The microswitch 30, once operated, may decouple the electromagnetic coupling 11 or operate in any other convenient known manner for stopping the rolling mill.

It is also clear that by suitably setting the depth of the groove 27 it is possible to predetermine the value of the stress caused by the rolled material which will cause the screws 26 to break and hence the expulsion of the guide 25.

Considering now FIG. 5, in which parts equal to those of FIG. 4 are indicated with the same reference numerals, the guide 25 is slidably mounted in a suitable bush 33 fixed rigidly to the housing 23 by screws 34. The guide 25 is however locked to the bush 33 by a suitable safety pin 35, arranged to be sheared by the thrust exerted on the front mouth -of the guide by the material when it begins to form the flower." In this case the rear edge of the guide 25 also comprises a convenient chamfer for engaging the projecting end of the operating rod 31 of the microswitch 30.

It is to be understood that the embodiments described are only two possible and preferred embodiments of the present invention and that conceptually and mechanically equivalent modifications are possible without leaving the scope of the invention.

What we claim is:

l. A safety device for rolling mills arranged to interrupt the transmission of motion from the motor to the rolling stands, in which the outlet guide for the rolled material of at least the last stand of the rolling mill is fixed to the housing of the respective stand by fixing means arranged to allow the guide to separate from the housing when said fixing means are subjected to a thrust greater than a predetermined value, said outlet guide being arranged to engage switch means for interrupting the transmission of motion from the motor to the rolling stands.

2. A device as claimed in claim 1, in which said fixing means consist of screws having a weakened zone for starting the fracture when the outlet guide is thrust axially in a direction away from the housing of the rolling stand.

3. A device as claimed in claim 1, in which said outlet guide is slidably mounted in a bush fixed rigidly to the housing of the rolling stand, said guide being fixed to said bush by means of a shearable pin.

4. A device as claimed in claim 1, in which the outlet guides of all the rolling stands can be separated from their respective housings by a thrust acting axially on the guide.

5. A device as claimed in claim 1, in which all the rolling stands are provided with a separable outlet guide as heretofore claimed.

6. A device as claimed in claim 1, in which said switch means are connected so as to disengage the electromagnetic connecting clutch between the motor and drive pinion of the kinematic transmission chain. 

1. A safety device for rolling mills arranged to interrupt the transmission of motion from the motor to the rolling stands, in which the outlet guide for the rolled material of at least the last stand of the rolling mill is fixed to the housing of the respective stand by fixing means arranged to allow the guide to separate from the housing when said fixing means are subjected to a thrust greater than a predetermined value, said outlet guide being arranged to engage switch means for interrupting the transmission of motion from the motor to the rolling stands.
 2. A device as claimed in claim 1, in which said fixing means consist of screws having a weakened zone for starting the fracture when the outlet guide is thrust axially in a direction away from the housing of the rolling stand.
 3. A device as claimed in cLaim 1, in which said outlet guide is slidably mounted in a bush fixed rigidly to the housing of the rolling stand, said guide being fixed to said bush by means of a shearable pin.
 4. A device as claimed in claim 1, in which the outlet guides of all the rolling stands can be separated from their respective housings by a thrust acting axially on the guide.
 5. A device as claimed in claim 1, in which all the rolling stands are provided with a separable outlet guide as heretofore claimed.
 6. A device as claimed in claim 1, in which said switch means are connected so as to disengage the electromagnetic connecting clutch between the motor and drive pinion of the kinematic transmission chain. 